The present invention relates to apparatus and method for detecting defects such as tears, holes or the like in a moving web, such as a textile fabric, evaluating the location and magnitude of the defect and providing control signals responsive thereto.
Webs of material, particularly textile materials such as woven or knitted fabrics are generally characterized as first or second quality goods, depending upon the number of structural or other defects appearing in a predetermined length of the web, and/or the size of the defects. It is obviously significant in the processing of moving textile or other webs that structural defects such as rips, tears, holes or the like, depending upon the location and size of same cannot only create second quality goods, but also can create processing problems. In fact, such defects can worsen during further processing to a point where the web is totally separated and/or to a point where damage to the web becomes adequately great that a process being performed thereon becomes fouled.
Additionally, where long, basically indeterminate lengths of a web, are being joined or batched to provide a continuously operating process, shorter lengths of web are physically sewn together to achieve a large batch. Often the seams are sewn by manual operation of a sewing machine which can lead to faulty seams. In general therefore, webs such as textile material, are fragile to an extent that the web may be cut, slit, torn, or a seam separated, or the like all of which as mentioned above, can lead to a lessening of quality of the goods and thus lower the price of same, or unwanted interruptions of processing equipment such as a finishing range, dyeing range, printing machine or the like.
Hence it is quite important that when a significant length of a textile material is to be fed to a tenter frame, dye range, print machine or the like that the web be free of significant defects both from a standpoint of overall quality and continued operation of the equipment. Furthermore, a particular defect in a moving web may be the product of malfunction of prior process equipment, which if not corrected, may lead to repetitive defects in successive lengths of web being processed thereon.
Furthermore, depending upon a particular type defect in a web, its location and size, one, if knowledgeable of such particular defect may render an independent judgement as to whether the defect is likely to create a problem downstream, will definitely create a problem downstream, or is not likely to create a problem downstream. For example, a very small tear or cut in the selvage of a textile fabric is most likely to continue across the width of the web, thus constituting a type defect that should require immediate attention. Conversely, a moderate but significantly larger cut, tear, rip or the like located in the middle of the web is likely to create a problem downstream only if the defect is significant in size as to endanger the structural integrity of the web, or to present problems to the downstream processing equipment. Upon detection of such a defect, a judgment call needs to be made to ascertain whether the defect can pass or whether the particular processing equipment on which the detector is located should be stopped and the defect corrected, or cut from the moving web followed by a reseaming. Still further, a very small rip or tear at a particular medial location on the web is not likely to create a problem at all, and can perhaps be summarily dismissed without any further judgment and without interruption of the operation of the machine.
Heretofore detection apparatus has been available for determining the existence of a defect in a moving web, and after detection, bringing about stoppage of the process equipment in combination with the actuation of an audible alarm, light or the like to signal to an operator that a defect has been found. At such time, the operator would approach the process equipment and determine what, if any action should be taken with respect to the particular defect, based on his experience. In general such prior defect detectors have included photocells, lasers and the like that are stationarily mounted across the path of a moving web, that themselves move across the path of a moving web, that scan the web, or which are otherwise situated to monitor at least a representative area of the web. Such detectors have, in general, been utilized in conjunction with a dedicated light source to be sensed. In like fashion, other electronic sensors have been utilized for defect detection.
Heretofore, defect detectors, as noted above, have not eliminated the need for an individual to remain at the inspection site for a majority of the time, but have primarily been utilized to eliminate the need for an inspector or inspectors as the case may be, to physically view the entire web as it passes through an inspection station. In fact, for high tech end uses, or other fabrics where the quality of same is critical, it is still a general rule rather than an exception, that one or more operators physically man an inspection station and view the entirety of a length of web being processed.
The present invention is addressed to the same type problems as prior art detectors, though from a standpoint of operation and efficiency overcomes problems noted above. In fact, the present invention achieves not only correct detection of both location and magnitude of a defect, but also can control web process equipment responsive thereto. There is no known prior art that is believed to anticipate or suggest the subject matter of the present invention.